lm317

[Rob]

Paul Perry wrote:
> 
> At 02:51 PM 17/12/98 -0600, Rob <cyborg0 wrote:
> 
> >Hey, anybody know how to boost the stability and current handling of an
> >already existing lm317 circuit? Can you just piggyback another lm317?
> 
> You certainly cant run regs in paralel.
> You can add/improve heatsinking or use a to3 version.
> But, the best thing is to have a sep reg for part of the system, which
> improves isolation.
> 
Well I have found you can run regs in parallel, to my surprise!!.. I
thought by what I knew about how they work, that this *might* be a
possibility, although I thought it might cause other problems..
Sure enough, after paging through a few textbooks and circuit source
books, in one of the books I have, encyclopaedia of electronic circuits,
vol3, page 489, they have a way to piggyback lm317s! mind you, you have
to add a lm317, two 1n4002s, and a 10uf/35v cap, but thats not really
much and you wouldnt even have to cut any traces! This boosts the lm317
circuit to 3A.. This is very good info. 
Does it work? I dont know yet..more on this later, since I need to map
out the specifics of my PCB lm317 based supply. Actually, all this mod
requires is jumpering various elements of the existing lm317 with
1n4002s and a cap. The extra lm317 lays directly on top of the existing
one! Really cool.. :))

> >Increase the capacitor in the circuit?
> If it's big enough, more won't help.

>From what I see, you are right about that.. I *guess* you could decrease
the initial droop a little bit by increasing the cap on the input of the
lm317, but thats about it..
Rob